Electric instruments have been required to have higher performance and higher reliability, such as smaller size and higher heat resistance. Along with this, insulating materials used in electric instruments have also been required to have excellent chemical stability at high temperatures. Especially incases where an insulating material is applied to the stator coil of a rotating electric machine for the purpose of insulation, in general, the crosslink density of a cured product is often increased to improve the heat resistance.
For example, Patent Document 1 provides a thermosetting resin composition including at least an aminomaleimide compound obtained through a reaction among an α-ketonitrile compound having at least two α-ketonitrile groups, a maleimide compound having at least two maleimide groups, and an amine having at least two amino groups, to thereby improve the heat resistance.
Patent Document 2 provides an epoxy resin composition including a multifunctional epoxy resin and a curing agent for an epoxy resin, the multifunctional epoxy resin being obtained through a reaction between: a mixture of a bifunctional epoxy resin including as a skeleton a specific bisphenol such as bisphenol A and a resorcinol-based novolac resin; and a specific bisphenol, to thereby improve the mechanical strength and flexibility as well as the heat resistance.
Patent Document 3 provides a resin composition including a bisphenol-based epoxy resin, a cresol novolac-based epoxy resin, and an alicyclic epoxy resin, together with a polysulfide-modified epoxy resin serving as a flexibilizer, to thereby improves the heat resistance and flexibility.
Patent Document 1: Japanese Patent Application laid-open No. 60-152528
Patent Document 2: Japanese Patent Application laid-open No. 63-48323
Patent Document 3: Japanese Patent Application laid-open No. 7-207123